Display device and driving method thereof

ABSTRACT

A display device includes a driver connected to a display panel and transmitting scan signals or data signals to the display panel, a frame memory connected to the driver, storing image data and transmitting at least some of the image data to the driver, and a controller connected to the driver and the frame memory, generating a control signal and transmitting the control signal to the driver or the frame memory, wherein each of the sub-fields includes an address period in which the scan signals are transmitted to the respective pixel rows, the controller transmits the control signal to the driver to transmit the scan signals to the pixel rows during a current frame such that the scan signals corresponding to the current frame are transmitted after, among the image data corresponding to the current frame, the image data corresponding to the pixel rows are stored in the frame memory.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2012-0105321 filed on Sep. 21, 2012 in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND

1. Field

The following description relates to a display device and a drivingmethod thereof, and more particularly, to a display device and a drivingmethod thereof, which can prevent or protect a tearing effect fromoccurring.

2. Description

Along with development of information communication technology anddemand of diversified information society, there is increasing demandfor displays. Instead of cathode ray tube (CRT) display devices, flatpanel display devices (FPDs)are being developed according to the demandfor compact and power-saving displays. Examples of the currently widelyused FPD include an electroluminescent display (ELD), a liquid crystaldisplay (LCD), such as TFT-LCD or TN/STN LCD, a plasma display device,and so on.

In the FPD, gray scales may be represented in an analog or digitalmanner. In the digital manner, the gray scales are represented bydividing one frame into a plurality of sub-fields and making pixels emitlight or not during a period corresponding to each of the sub-fields.That is, according to the digital gray scale representing method, thegray scales are represented by adjusting the emission period of pixelswithin one frame.

The FPD may include a frame memory storing image data to be displayed.When a speed of writing the image data in the frame memory is differentfrom a speed of reading the image data from the frame memory, the FPDmay emit light from some of the plurality of pixels according to imagedata of the previous frame, and emit light from the other of theplurality of pixels according to image data of the current frame. Inother words, a phenomenon that an image appears to be torn may occur,which is referred to as a “tearing effect.”

SUMMARY

An aspect of an embodiment of the present invention is directed toward adisplay device and a driving method thereof, which can prevent (orprotect from) a tearing effect.

An aspect of an embodiment of the present invention is directed toward adisplay device and a driving method thereof, which can prevent (orprotect) a tearing effect using only a single frame memory without usingadditional frame memory.

The above and other objects of the present invention will be describedin or be apparent from the following description of the exemplaryembodiments.

According to an embodiment of the present invention, there is provided adisplay device including: a display panel including a plurality of pixelrows; a driver connected to the display panel and transmitting scansignals or data signals to the display panel; a frame memory connectedto the driver, storing externally received image data and transmittingat least some of the image data to the driver; and a controllerconnected to the driver and the frame memory, generating a controlsignal and transmitting the control signal to the driver or the framememory, wherein each of the sub-fields includes an address period inwhich the scan signals are transmitted to the respective pixel rows, andthe controller transmits the control signal to the driver to transmitthe scan signals to the pixel rows during a current frame such that thescan signals corresponding to the current frame are transmitted after,among the image data corresponding to the current frame, the image datacorresponding to the pixel rows are stored in the frame memory.

The controller may transmit the control signal to the driver such that atotal time taken for the scan signals to be transmitted to all of theplurality of pixel rows during the address period of the sub-fieldarranged earliest during the current frame, among the plurality ofsub-fields, is longer than or equal to a time taken for the image datacorresponding to the current frame to be all stored in the frame memory.

The time taken for the image data corresponding to the current frame tobe all stored in the frame memory may be shorter than or equal to halfof the current frame.

The time taken for the image data corresponding to the current frame tobe all stored in the frame memory may be shorter than or equal to onefourth of the current frame.

In one embodiment, the data signal is transmitted from the driver to thedisplay panel for the address period of each of the sub-fields; theplurality of sub-fields include first to nth sub-fields, where n is anatural number of 2 or greater, arranged according to the timingsequence within the current frame; and the data signal transmitted tothe display panel during the address period of the first sub-field andthe data signal transmitted to the display panel during the addressperiod of the nth sub-field are equal to each other.

The data signal may be transmitted from the driver to the display panelfor the address period of each of the sub-fields; and one of m databits, where m is a natural number of 2 or greater, may be transmittedfrom the driver to the display panel.

In one embodiment, the plurality of sub-fields include (m+1) sub-fields,the (m+1) sub-fields include first to (m+1)th sub-fields arrangedaccording to the timing sequence within the current frame, and the databit transmitted to the display panel during the address period of thefirst sub-field and the data bit transmitted to the display panel duringthe address period of the nth sub-field are equal to each other.

In one embodiment, the m data bits have weights, respectively, and thedata bit transmitted to the display panel during the address period ofthe first sub-field and the data bit transmitted to the display panelduring the address period of the (m+1)th sub-field have the highestweight among the m data bits.

The m data bits may include first to mth data bits, and an ith data bit,where 1<=i<=m, among the first to mth data bits, has a weight of2^(i−1).

In one embodiment, each of the pixel rows includes one or more pixels,and each of the first to (m+1)th sub-fields further includes a lightemission period in which the pixels emit light or not according to thedata bit transmitted to the display panel during the address periodincluded in each of the first to (m+1)th sub-fields.

A sum of the length of the light emission period of the first sub-fieldand the length of the light emission period of the (m+1)th sub-field foreach of the pixel rows may be equal to each other.

The length of the light emission period of the first sub-field or thelength of the light emission period of the (m+1)th sub-field for each ofthe pixel rows may be different from each other.

In one embodiment, the m data bits have weights, respectively, lengthsof the light emission periods of the second to mth sub-fields areproportional to weights of the data bits transmitted to the displaypanel during the address periods included in the second to mthsub-fields, and a sum of the lengths of the light emission periods ofthe first and (m+1)th sub-fields is proportional to the weight of thedata bit transmitted to the display panel during the address periodincluded in the first sub-field or the (m+1)th sub-field.

The data bit transmitted to the display panel during the address periodof the first sub-field and the data bit transmitted to the display panelduring the address period of the (m+1)th sub-field may have the highestweight among the m data bits.

According to another embodiment of the present invention, there isprovided a driving method of a display device, the driving methodincluding a display device for displaying an image by dividing one frameinto a plurality of sub-fields, the display device including: a displaypanel including a plurality of pixel rows; a driver connected to thedisplay panel and transmitting scan signals or data signals to thedisplay panel; a frame memory connected to the driver, storingexternally received image data and transmitting at least some of theimage data to the driver; and a controller connected to the driver andthe frame memory, generating a control signal and transmitting thecontrol signal to the driver or the frame memory, wherein the controllertransmits the control signal to the driver such that a total time takenfor the scan signals to be transmitted to all of the plurality of pixelrows during an address period of the sub-field arranged earliest duringa current frame, among the plurality of sub-fields, is longer than orequal to a time taken for the image data corresponding to the currentframe to be all stored in the frame memory.

All of the scan signals transmitted during the current frame may startto be transmitted to the display panel after the frame memory starts toreceive the image data corresponding to the current frame.

The time taken for the image data corresponding to the current frame tobe all stored in the frame memory may be shorter than or equal to halfof the current frame.

In one embodiment, the data signal is transmitted from the driver to thedisplay panel for the address period of each of the sub-fields; one of mdata bits, where m is a natural number of 2 or greater, is transmittedfrom the driver to the display panel; the plurality of sub-fieldsinclude first to (m+1)th sub-fields, where m is a natural number of 2 orgreater, arranged according to the timing sequence within the currentframe; and the data signal transmitted to the display panel during theaddress period of the first sub-field and the data signal transmitted tothe display panel during the address period of the (m+1)th sub-field areequal to each other.

In one embodiment, each of the pixel rows includes one or more pixels,each of the first to (m+1)th sub-fields further includes a lightemission period in which the pixels emit light or not according to thedata bit transmitted to the display panel during the address periodincluded in each of the first to (m+1)th sub-fields, and a sum of thelength of the light emission period of the first sub-field and thelength of the light emission period of the (m+1)th sub-field for each ofthe pixel rows is equal to each other.

In one embodiment, the m data bits have weights, respectively; andlengths of the light emission periods of the second to mth sub-fieldsare proportional to weights of the data bits transmitted to the displaypanel during the address periods included in the second to mthsub-fields; and a sum of the lengths of the light emission periods ofthe first and (m+1)th sub-fields is proportional to the weight of thedata bit transmitted to the display panel during the address periodincluded in the first sub-field or the (m+1)th sub-field; and the databit transmitted to the display panel during the address period of thefirst sub-field and the data bit transmitted to the display panel duringthe address period of the (m+1)th sub-field have the highest weightamong the m data bits.

According to an embodiment of the present invention, in the displaydevice and the driving method thereof, an image tearing effect can beprevented.

Also, according to an embodiment of the present invention, in thedisplay device and the driving method thereof, a tearing effect can beprevented using only a single frame memory without using additionalframe memory.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a circuit view illustrating a configuration of a displaydevice according to an embodiment of the present invention;

FIG. 2 is a circuit view illustrating a configuration of a pixel shownin FIG. 1;

FIG. 3 is a time-scanning line graph illustrating timings of scansignals during two neighboring frames according to a first embodiment ofthe present invention;

FIG. 4 is a time-scanning line graph illustrating timings of scansignals during two neighboring frames according to a second embodimentof the present invention;

FIG. 5 is a time-scanning line graph illustrating timings of scansignals during two neighboring frames according to a third embodiment ofthe present invention; and

FIG. 6 is a time-scanning line graph illustrating timings of scansignals during two neighboring frames according to a fourth embodimentof the present invention.

DETAILED DESCRIPTION

Advantages and features of the present invention and methods ofaccomplishing the same may be understood more readily by reference tothe following detailed description of exemplary embodiments and theaccompanying drawings. The present invention may, however, be embodiedin many different forms and should not be construed as being limited tothe embodiments set forth herein. Rather, these embodiments are providedso that this disclosure will be thorough and complete and will fullyconvey the concept of the invention to those skilled in the art, and thepresent invention will only be defined by the appended claims. Thus, insome embodiments, well-known structures and devices are not shown inorder not to obscure the description of the invention with unnecessarydetail. Like numbers refer to like elements throughout. In the drawings,the thickness of layers and regions are exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on” or “connected to” another element or layer, it can bedirectly on or connected to the other element or layer, or one or moreintervening elements or layers may be present therebetween. In contrast,when an element is referred to as being “directly on” or “directlyconnected to” another element or layer, there is no intervening elementor layer present therebetween. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items.

Spatially relative terms, such as “below,” “beneath,” “lower,” “above,”“upper,” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures.

Embodiments described herein will be described referring to plan viewsand/or cross-sectional views by way of ideal schematic views of theinvention. Accordingly, the exemplary views may be modified depending onmanufacturing technologies and/or tolerances. Therefore, the embodimentsof the invention are not limited to those shown in the views, butinclude modifications in configuration formed on the basis ofmanufacturing processes. Therefore, regions exemplified in figures haveschematic properties and shapes of regions shown in figures exemplifyspecific shapes of regions of elements and do not limit aspects of theinvention.

Hereinafter, a display device according to an embodiment of the presentinvention and a driving method thereof will be described with referenceto the accompanying drawings.

The display device according to an embodiment of the present inventionmay be implemented by various kinds of display devices, including anorganic light emitting display (OLED) device, a plasma display panel(PDP), a field emission display, and so on. In the followingdescription, it is assumed that the display device is implemented by theOLED device, but aspects of the present invention are not limitedthereto. The driving method according to the embodiment of the presentinvention may be applied to various kinds of display devices.

FIG. 1 is a circuit view illustrating a configuration of a displaydevice according to an embodiment of the present invention. Referring toFIG. 1, the display device includes: a display panel 100 including oneor more pixels 101; a scan driver 400 connected to the display panel 100through scanning lines S1 to Sn, generating scan signals andtransmitting the same to the display panel 100; a data driver 300connected to the display panel 100 through data lines D1 to Dm,generating data signals and transmitting the same to the display panel100; a frame memory 200 connected to the data driver 300, storingexternally received image data and transmitting at least some of theimage data to the data driver 300; and a controller 500 connected to thescan driver 400, the data driver 300 and the frame memory 200,generating a control signal and transmitting the same to the scan driver400, the data driver 300 or the frame memory 200.

The display panel 100 may include one or more pixels 101. In a casewhere the display panel 100 includes a plurality of pixels 101, thepixels 101 may be arranged in a two-dimensional array of n rows and mcolumns.

The pixels 101 may be connected to the scanning lines S1 to Sn. The samenumber of scanning lines S1 to Sn as that of rows in an array of thepixels 101 may be arranged. The respective scanning lines S1 to Sn maybe connected to the respective rows in the array of the pixels 101 in aone-to-one corresponding relationship. That is, one of the scanninglines S1 to Sn may be connected to all of the pixels 101 included in onerow of the array of the pixels 101.

The pixels 101 may be connected to the data lines D1 to Dm. The samenumber of data lines D1 to Dm as that of columns in the array of thepixels 101 may be arranged. The respective data lines D1 to Dm may beconnected to the respective columns in the array of the pixels 101 in aone-to-one corresponding relationship. That is, one of the data lines D1to Dm may be connected to all of the pixels 101 included in one columnof the array of the pixels 101.

The pixels 101 may emit light according to the scan signals transmittedthrough the scanning lines S1 to Sn connected to the pixels 101, thedata signals transmitted through the data lines D1 to Dm connected tothe pixels 101, a first power supply ELVDD that is received from theoutside, and a second power supply ELVSS that is received from theoutside.

FIG. 2 is a circuit view illustrating a configuration of a pixel (101)shown in FIG. 1. Referring to FIG. 2, the pixel 101 may include a firsttransistor M1 including a first electrode, a second electrode and a gateelectrode, a second transistor M2 including a first electrode, a secondelectrode and a gate electrode, a capacitor Cst having one end andanother end, and an organic light emitting diode (OLED) having one endand another end. The first transistor M1 and the second transistor M2may be PMOS (p-channel metal oxide semiconductor) transistors or NMOS(n-channel metal oxide semiconductor transistors. In the followingdescription, it is assumed that the first transistor M1 and the secondtransistor M2 are both PMOS transistors.

The second transistor M2 may be turned on in response to the scansignals transmitted through the scanning lines S1 to Sn. If the secondtransistor M2 is turned on, the data signals transmitted through thedata lines D1 to Dm may fill the capacitor Cst. The capacitor Cstmaintains a voltage of the gate electrode of the first transistor M1.Therefore, the capacitor Cst may allow the intensity of current flowingfrom the first electrode to the second electrode of the first transistorM1 to be maintained at a constant level.

If the current flows from the first electrode to the second electrode ofthe first transistor M1, it may flow in the OLED connected between thefirst transistor M1 and the second power supply ELVSS. If the currentflows in the OLED, the OLED may emit light.

Referring back to FIG. 1, the scan driver 400 may be connected to thedisplay panel 100 through the scanning lines S1 to Sn. The scan driver400 may generate scan signals according to the control signaltransmitted from the controller 500 and then transmit the same to thedisplay panel 100.

The data driver 300 may be connected to the display panel 100 throughthe data lines. The data driver 300 may generate the data signalsaccording to the control signal transmitted from the controller 500. Thedata driver 300 may generate the data signals based on the image datatransmitted from the frame memory 200. The data driver 300 may transmitthe generated data signal to the display panel 100.

The frame memory 200 may be connected to the data driver 300. The framememory 200 may store the externally received image data and may provideat least some of the image data to the data driver 300.

The frame memory 200 may receive image data from the outside accordingto the control signal transmitted from the controller 500 and may storethe received image data. The frame memory 200 may have a memory sizeenough to store the image data corresponding to at least one frame. Theframe memory 200 may receive the image data corresponding to each framefrom the outside for each frame and may store the received image data.

For example, it is assumed that an image corresponding to one frameincludes n rows from first to nth rows. The frame memory 200 maysequentially receive the first to nth image data and may store the same.

The image data stored in the frame memory 200, specifically the imagedata corresponding to one row of the display panel 100, may betransmitted to the data driver 300 according to a horizontalsynchronization signal Hsync. In other words, image data may betransmitted to the data driver 300 sequentially from the image datacorresponding to the first row to the image data corresponding to thenth row by one row at a time for each Hsync.

After the image data corresponding to all of the rows of the displaypanel 100 are transmitted to the data driver 300, a verticalsynchronization signal Vsync may be transmitted from the controller 500.If the Vsync is transmitted, the image data may be again transmitted tothe data driver 300 sequentially from the image data corresponding tothe first row of the display panel 100 according to the Hsync.

The controller 500 may be connected to the scan driver 400, the datadriver 300 and the frame memory 200. The controller 500 may generate thecontrol signal and may transmit the same to the scan driver 400, thedata driver 300 or the frame memory 200. The controller 500 may generateVsync, Hsync, etc. and may transmit the same to the scan driver 400 orthe data driver 300. In addition, the controller 500 may generate thecontrol signal that allows the frame memory 200 to externally receiveand store image data and may then transmit the control signal to theframe memory 200.

FIG. 3 is a time-scanning line graph illustrating timings of scansignals during two neighboring frames according to a first embodiment ofthe present invention.

Referring to FIG. 3, the display device according to the firstembodiment of the present invention may represent gray scales of animage by adjusting the emission period of pixels 101 within one frame.To this end, one frame may include a plurality of sub-fields. The grayscales may be represented by allowing each of the pixels 101 to emitlight or not during a time period corresponding to each of the pluralityof sub-fields.

Data signals of a plurality of data bits may be transmitted to one ofthe pixels 101 during a time period corresponding to one frame. Forexample, as the data signals, m data bits may be transmittedsequentially from the first to mth data bits during a time periodcorresponding to one frame. The ith data bit, where 1<=i<=m, among thefirst to mth data bits may have a weight of 2^(i−1). A weight of eachdata bit may indicate a length of a relative emission period or arelative non-emission period within one frame. The least significantdata bit of the data to be transmitted as the data signal during thetime period corresponding to one frame may be the first data bit, andthe most significant data bit may be the mth data bit.

According to the first embodiment of the present invention, one framemay include sub-fields one more than the data bits included in the datasignals transmitted to one pixel 101 during the time periodcorresponding to one. That is, assuming that m data bits are transmittedas the data signals sequentially from the first to mth data bits, oneframe may include (m+1) sub-fields. The (m+1) sub-fields may includefirst to (m+1)th sub-fields.

Each of the sub-fields may include an address period, a light emissionperiod and an erasure period. In the address period of each sub-field,the scan signals may be transmitted to the respective rows of thedisplay panel 100. In the following description, the scan signaltransmitted to the display panel 100 in the address period of the ithsub-field, where 1<=i<=m+1, will be referred to as an ith scan signal.

Whenever the scan signal is transmitted to each row of the display panel100 during the address period, one of the plurality of data bits may betransmitted to the pixel 101 as the data signal. According to thisembodiment, the mth data bit may be transmitted when the first scansignal is transmitted in the address period of the first sub-field. Inaddition, the (i−1)th data bit may be transmitted to the pixel 101 whenthe ith scan signal is transmitted in the address period of the ithsub-field, where 2<=i<=m+1. That is, the mth data bit having the highestweight among the data bits may be transmitted to the pixel 101 when thefirst or (m+1)th scan signal is transmitted.

During one frame, the first sub-field may be arranged as the earliestsub-field and the (m+1)th sub-field may be arranged as the latestsub-field. That is, the first scan signal may be the earliesttransmitted scan signal to each row of the display panel 100 and the(m+1)th scan signal may be the latest arranged scan signal. Therefore,among the plurality of data bits included in the data signal, the mthdata bit having the highest weight may be earliest transmitted to eachrow of the display panel 100 and may be latest transmitted again duringone frame.

The remaining second to mth sub-fields may be arranged between the firstsub-field and the (m+1)th sub-field. The second to mth sub-fields may bearranged in any possible order. In other words, the second to mth scansignals may be transmitted after the first scan signal is transmittedand before the (m+1)th scan signal is transmitted. The second to mthscan signals may be transmitted in any possible order.

Lengths of address periods included in the first to (m+1)th sub-fieldsmay be equal to each other.

The address periods of one sub-field may be arranged sequentially fromthe first to nth rows of the display panel 100. In other words, the scansignals and data bits for one sub-field may be transmitted sequentiallyfrom the first to nth rows of the display panel 100.

However, a total time taken for the scan signals and the data bits to betransmitted sequentially from the first row to the nth row of thedisplay panel 100 is as follows.

The total time taken for the first scan signal for the first sub-fieldto be transmitted sequentially from the first row to the nth row of thedisplay panel 100 may be longer than or equal to a time taken for theimage data corresponding to one frame to be all stored in the framememory 200. The time taken for the image data corresponding to one frameto be all stored in the frame memory 200 may be shorter than or equal tohalf of the time for one frame.

For example, assuming that a display device displays 60 frames persecond, the time period corresponding to one frame may be 1/60 seconds.Therefore, the time taken for the image data corresponding to one frameto be all stored in the frame memory 200 may be shorter than or equal to1/120 seconds. In addition, a total time taken for the first scan signalfor the first sub-field to be transmitted sequentially from the firstrow to the nth row of the display panel 100 may be longer than or equalto 1/120 seconds.

A total time taken for the second to (m+1)th scan signals to betransmitted sequentially from the first to nth rows of the display panel100 may be made to be as short as possible.

It is assumed that the frame memory 200 has a memory size enough tostore only the image data corresponding to one frame. It is also assumedthat the frame memory 200 may receive the image data corresponding tothe current frame sequentially from the first to nth rows at the sametime when the period of the current frame starts.

If the total time taken for the scan signals and the data bits to betransmitted sequentially from the first row to the nth row of thedisplay panel 100 is shorter than the time taken for the image datacorresponding to one frame to be all written in the frame memory 200,the following problem may arise.

The display panel 100 may emit light from some of the plurality ofpixels 101 according to image data of the previous frame, and emit lightfrom the other of the plurality of pixels 101 according to image data ofthe current frame. In other words, a phenomenon that an image appears tobe torn, which is called a “tearing effect,” may occur.

For example, it is assumed that the scan signals and data signals startto be transmitted sequentially from the first row of the display panel100 after the frame memory 200 starts to receive the image datacorresponding to the current frame. It is also assumed that transmittingof the scan signals and data signals sequentially from the first to nthrow of the display panel 100, after the frame memory 200 completelyreceives all of the image data corresponding to the current frame. Inthis case, the total time taken for the scan signals and the data bitsto be transmitted sequentially from the first row to the nth row of thedisplay panel 100 may be shorter than the time taken for the image datacorresponding to one frame to be all received by the frame memory 200.

It is assumed that when the scan signal and data signal are transmittedto the (k−1)th row of the display panel 100, where 1<k<n, the image datacorresponding to the (k−1)th row of the current frame has already beenwritten in the frame memory 200. It is also assumed that when the scansignal and data signal are transmitted to the kth row of the displaypanel 100, the image data corresponding to the kth row of the currentframe has yet to be written on the frame memory 200.

The display panel 100 may emit light from the pixels 101 included in thefirst to (k−1)th rows of the display panel 100 according to the imagedata of the current frame. In addition, the display panel 100 may emitlight from the pixels 101 included in the kth to nth rows of the displaypanel 100 according to the image data of the previous frame. Therefore,a phenomenon that an image appears to be torn, which is called a“tearing effect,” may occur.

In the embodiment of the present invention, the frame memory 200receives the image data corresponding to the current frame sequentiallyfrom the first to nth rows at the same time when the period of thecurrent frame starts. In addition, immediately after the frame memory200 starts to receive the image data corresponding to the current frame,the first scan signal for the first sub-field may start to betransmitted to the display panel 100. In addition, the total time takenfor the first scan signal for the first sub-field to be transmittedsequentially from the first to nth rows of the display panel 100 may belonger than or equal to the time taken for the image data correspondingto the current frame to be all received by the frame memory 200.

Therefore, in the display device according to this embodiment, as shownin FIG. 3, the first to (m+1)th scan signals may be transmitted to therespective rows of the display panel 100 after the image datacorresponding to the respective rows of the current frame are receivedby the frame memory 200. That is, for all of the rows of the displaypanel 100, the first to (m+1)th scan signals may be all transmitted tothe display panel 10 after the image data corresponding to the currentframe are received by the frame memory 200. Therefore, a tearing effectcan be prevented.

During a light emission period of each sub-field, the pixel 101 may emitlight or may not emit light. The pixel 101 may emit light or may notemit light during the light emission period according to the value ofthe data bit transmitted through the data lines D1 to Dm when the scansignal is transmitted during the address period. For example, if thevalue of the transmitted data bit is at a low level, the pixel 101 mayemit light during the light emission period. If the value of thetransmitted data bit is at a high level, the pixel 101 may not emitlight during the light emission period.

In other words, when the scan signal is transmitted during the addressperiod, the display panel 100 is controlled to emit light from the pixel101 or not according to the values of the data bits transmitted from thedata lines D1 to Dm. In addition, an emission state or a non-emissionstate of the pixel 101 may be sustained according to the values of thedata bits during the light emission period.

Therefore, a length of the light emission period of each of the first to(m+1)th sub-fields may indicate an emission period or a non-emissionperiod of each sub-field. Lengths of light emission periods included inthe first to (m+1)th sub-fields may be as follows.

The lengths of the light emission periods included in the second to mthsub-fields may be proportional to weights of the data bits transmittedduring the address periods included in the second to mth sub-fields. Inother words, the (i−1th data bit may be transmitted during the addressperiod of the ith sub-field, where 2<=i<=m, and the length of the lightemission period of the ith sub-field is proportional to 2^(i−2). Forexample, when m is 3 or greater, the light emission period of the thirdsub-field may be two times longer than the light emission period of thesecond sub-field, and the light emission period of the mth sub-field maybe 2^(m−2) times longer than the light emission period of the secondsub-field.

The lengths of the respective light emission periods included in thesecond to mth sub-fields may be equal to each other for all of the rowsof the display panel 100.

The length of the light emission period of the first sub-field or thelength of the light emission period of the (m+1)th sub-field for each ofthe rows in the display panel 100 may be different from each other.However, a sum of the length of the light emission period of the firstsub-field and the length of the light emission period of the (m+1)thsub-field for each of the rows in the display panel 100 may be equal toeach other.

In addition, the sum of the lengths of the light emission periods of thefirst and (m+1)th sub-fields may be equal to the weight of the data bittransmitted during the address period of the first sub-field or the(m+1)th sub-field. As described above, during both of the addressperiods of the first and (m+1)th sub-fields, the mth data bit may betransmitted. Therefore, the sum of the lengths of the light emissionperiods of the first and (m+1)th sub-fields may be proportional to2^(m−1).

For example, when m is 3 or greater, the sum of the lengths of the lightemission periods of the first and (m+1)th sub-fields may be 2^(m−1)times greater than the length of the light emission period of the secondsub-field. In addition, the sum of the lengths of the light emissionperiods of the first and (m+1)th sub-fields may be two times greaterthan the length of the light emission period of the mth sub-field.

Referring to FIG. 3, as described above, a total time taken for thefirst scan signal for the first sub-field to be transmitted sequentiallyfrom the first to nth rows of the display panel 100 may be longer thanor equal to a time taken for the image data corresponding to one frameto be all written in the frame memory 200. On the other hand, a totaltime taken for the second to (m+1)th scan signals to be transmittedsequentially from the first to nth rows of the display panel 100 may bemade to be as short as possible.

Therefore, as shown in FIG. 3, the length of the light emission periodof the first sub-field may be decreased for the respective rows of thedisplay panel 100 gradually from the first to nth rows of the displaypanel 100. In addition, the length of the light emission period of the(m+1)th sub-field may be increased for the respective rows of thedisplay panel 100 gradually from the first to nth rows of the displaypanel 100. In addition, a sum of the length of the light emission periodof the first sub-field and the length of the light emission period ofthe (m+1)th sub-field for each of the rows in the display panel 100 maybe equal to each other.

In the aforementioned display device according to this embodiment,during one frame, a set or predetermined data bit may be earliesttransmitted to each row of the display panel 100 and may be latestarranged again. The set or predetermined data bit may be a data bithaving the highest weight among the plurality of data bits each having aweight to represent gray scales of an image. Therefore, a total oflengths of the light emission periods for the plurality of data bits maybe proportional to weights of the respective data bits. In addition,after the image data corresponding to the current frame are received bythe frame memory 200, all of the scan signals may be transmitted to thedisplay panel 100 for all of the rows of the display panel 100.Therefore, a tearing effect can be prevented by using only the framememory 200 while maintaining display quality of the display device.

In an erasure period of each sub-field, the data signals stored in thecapacitor Cst of the pixel 101 may be erased. Even if an emission stateof the pixel 101 is sustained during the light emission period, emissionof the pixel 101 may be interrupted through the erasure period. Lengthsof the respective erasure periods included in the first to (m+1)thsub-fields may be the same with each other.

FIG. 4 is a time-scanning line graph illustrating timings of scansignals during two neighboring frames according to a second embodimentof the present invention.

Referring to FIG. 4, in the second embodiment of the present invention,a time taken for the image data corresponding to one frame to be allwritten in a frame memory 200 may be shorter than or equal to ¼ of atime period corresponding to one frame.

For example, assuming that the display device displays 60 frames persecond, the time period corresponding to one frame may be 1/60 seconds.Therefore, the time taken for the image data corresponding to one frameto be all written in the frame memory 200 may be shorter than or equalto 1/240 seconds. In addition, a total time taken for the first scansignal for the first sub-field to be transmitted sequentially from thefirst row to the nth row of the display panel 100 may be longer than orequal to 1/240 seconds.

Since the remaining contents are the same as those of the firstembodiment, repeated descriptions will be omitted.

FIG. 5 is a time-scanning line graph illustrating timings of scansignals during two neighboring frames according to a third embodiment ofthe present invention.

Referring to FIG. 5, in the third embodiment of the present invention,address periods of first sub-fields may be arranged sequentially fromfirst to nth rows of a display panel 100. In other words, scan signalsand data bits for the first sub-field may be transmitted sequentiallyfrom first to nth rows of the display panel 100.

A total time taken for the first scan signal for the first sub-field tobe transmitted sequentially from the first to nth rows of the displaypanel 100 may be shorter than or equal to a time taken for the imagedata corresponding to one frame to be all written in a frame memory 200.The time taken for the image data corresponding to one frame to be allwritten in the frame memory 200 may be shorter than or equal to half ofthe time period corresponding to one frame.

The frame memory 200 may receive the image data corresponding to thecurrent frame sequentially from the first to nth rows at the same timewhen the period of the current frame starts. In addition, immediatelyafter the frame memory 200 starts to receive the image datacorresponding to the current frame, the first scan signal for the firstsub-field may start to be transmitted to the display panel 100.

However, unlike in the first embodiment, in the third embodiment,address periods of the second to (m+1)th sub-fields may be arranged inan arbitrary order from the first to Ith rows of the display panel 100.

A length of the first sub-field for a certain row included in thedisplay panel 100 may vary according to the timing sequence of theaddress periods of the first and second sub-fields for the certain row.

For example, referring to FIG. 5, the address period of the secondsub-field for the first row may be arranged later than that of thesecond sub-field for the second row. In addition, the address period ofthe second sub-field for the first row may be arranged earlier than thatof the second sub-field for the third row. The light emission period ofthe first sub-field for the third row may be longer than that of thefirst sub-field for the second row and may be shorter than that of thefirst sub-field for the first row.

In addition, a length of the light emission period of the (m+1)thsub-field for a certain row included in the display panel 100 may varyaccording to the timing positions of the address period of the (m+1)thsub-field for the certain row and the address period of the firstsub-field for the next frame.

However, a sum of the length of the light emission period of the firstsub-field and the length of the light emission period of the (m+1)thsub-field, for each of the rows in the display panel 100, is equal toeach other. Therefore, the timing sequence in which the address periodsof the (m+1)th sub-fields for the respective rows included in thedisplay panel 100 are arranged may be the same as that of the secondsub-fields for the respective rows included in the display panel 100.

For example, referring to FIG. 5, the address period of the (m+1)thsub-field for the first row may be arranged later than that of the(m+1)th sub-field for the second row. In addition, the address period ofthe (m+1)th sub-field for the first row may be arranged earlier thanthat of the (m+1)th sub-field for the third row. A sum of the lengths ofthe light emission periods of the first and (m+1)th sub-fields for acertain row may be equal to that for the other rows.

Since the remaining contents are the same as those of the firstembodiment, repeated descriptions will be omitted.

FIG. 6 is a time-scanning line graph illustrating timings of scansignals during two neighboring frames according to a fourth embodimentof the present invention.

Referring to FIG. 6, in the fourth embodiment of the present invention,address periods of first sub-fields may be arranged sequentially fromfirst to nth rows of a display panel 100. In other words, scan signalsand data bits for the first sub-field may be transmitted sequentiallyfrom first to nth rows of the display panel 100.

A total time taken for the first scan signal for the first sub-field tobe transmitted sequentially from the first to nth rows of the displaypanel 100 may be shorter than or equal to a time taken for the imagedata corresponding to one frame to be all written in a frame memory 200.The time taken for the image data corresponding to the one frame to beall written in the frame memory 200 may be shorter than or equal to halfof the time period corresponding to the one frame.

The frame memory 200 may receive the image data corresponding to thecurrent frame sequentially from the first to nth rows at the same timewhen the period of the current frame starts. In addition, immediatelyafter the frame memory 200 starts to receive the image datacorresponding to the current frame, the first scan signal for the firstsub-field may start to be transmitted to the display panel 100.

Also, in this embodiment, the address periods of the (m+1)th sub-fieldmay be arranged sequentially from the first to nth rows of the displaypanel 100. In other words, scan signals and data bits for the (m+1)thsub-field may be transmitted sequentially from first to nth rows of thedisplay panel 100.

A total time taken for the (m+1)th scan signal to be transmitted fromthe first to nth rows of the display panel 100 may be made to be asshort as possible.

Erasure periods of the first sub-field may be arranged sequentially fromthe first to nth rows of a display panel 100. In other words, a timelength between a timing position at which the erasure period of thefirst sub-field for the first row and a timing position at which theerasure period of the first sub-field for the nth row, may be equal to atime length between a timing position at which the (m+1)th scan signalis transmitted to the first row and a timing position at which the(m+1)th scan signal is transmitted to the nth row.

However, unlike in the first embodiment, in the fourth embodiment,address periods of the second to mth sub-fields may be arranged in anarbitrary order from the first to nth rows of the display panel 100.

After the erasure period of the first sub-field starts and before thelight emission period of the second sub-field, a non-emission state ofthe pixel 101 may be sustained. In addition, after the erasure period ofthe mth sub-field starts and before the light emission period of the(m+1)th sub-field, a non-emission state of the pixel 101 may besustained.

The length of the light emission period of the first sub-field or thelength of the light emission period of the (m+1)th sub-field for each ofthe rows in the display panel 100 may be different from each other.However, a sum of the length of the light emission period of the firstsub-field and the length of the light emission period of the (m+1)thsub-field for each of the rows in the display panel 100 may be equal toeach other.

For example, referring to FIG. 6, lengths of the light emission periodsof the first sub-field for the respective rows included in the displaypanel 100 may be decreased gradually from the first to nth rows of thedisplay panel 100. In addition, lengths of the light emission periods ofthe (m+1)th sub-field for the respective rows included in the displaypanel 100 may be increased gradually from the first to nth rows of thedisplay panel 100. In addition, a sum of the lengths of the lightemission periods of the first and (m+1)th sub-fields for the certain rowincluded in the display panel 100 may be equal to that for the otherrows included in the display panel 100.

Since the remaining contents are the same as those of the firstembodiment, repeated descriptions will be omitted.

In the aforementioned display device according to this embodiment,during one frame, a set or predetermined data bit may be earliesttransmitted to each row of the display panel 100 and may be latestarranged again. The set or predetermined data bit may be a data bithaving the highest weight among the plurality of data bits each having aweight to represent gray scales of an image. Therefore, a total oflengths of the light emission periods included in the plurality of databits may be proportional to weights of the respective data bits. Inaddition, after the image data corresponding to the current frame arereceived by the frame memory 200, all of the scan signals may betransmitted to the display panel 100 for all of the rows of the displaypanel 100. Therefore, a tearing effect can be prevented by using onlythe frame memory 200 while maintaining display quality of the displaydevice.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims. It istherefore desired that the present embodiments be considered in allrespects as illustrative and not restrictive, reference being made tothe appended claims rather than the foregoing description to indicatethe scope of the invention, and equivalents thereof.

What is claimed is:
 1. A display device for displaying an image bydividing one frame into a plurality of sub-fields, the display devicecomprising: a display panel comprising a plurality of pixel rows; adriver connected to the display panel and for transmitting scan signalsor data signals to the display panel; a frame memory connected to thedriver, for storing externally received image data, and for transmittingat least some of the image data to the driver; and a controllerconnected to the driver and the frame memory, for generating a controlsignal and transmitting the control signal to the driver or the framememory, wherein each of the sub-fields includes an address period inwhich the scan signals are transmitted to the respective pixel rows,wherein the frame memory is configured to receive at least some of theimage data corresponding to a current frame from the respective pixelrows at the same time when the period of the current frame starts; andwherein the driver is configured to start to transmit scan signals forthe plurality of sub-fields to the display panel after the frame memorystarts to receive the image data corresponding to the current frame, thecontroller is configured to transmit the control signal to the driver totransmit the scan signals to the pixel rows during the current framesuch that the scan signals corresponding to the current frame aretransmitted after, among the image data corresponding to the currentframe, the image data corresponding to the pixel rows are stored in theframe memory.
 2. The display device of claim 1, wherein the controlleris configured to transmit the control signal to the driver such that atotal time taken for the scan signals to be transmitted to all of theplurality of pixel rows during the address period of the sub-fieldarranged earliest during the current frame, among the plurality ofsub-fields, is longer than or equal to a time taken for the image datacorresponding to the current frame to be all stored in the frame memory.3. The display device of claim 2, wherein the time taken for the imagedata corresponding to the current frame to be all stored in the framememory is shorter than or equal to half of the time period correspondingto one frame.
 4. The display device of claim 2, wherein the time takenfor the image data corresponding to the current frame to be all storedin the frame memory is shorter than or equal to one fourth of the timeperiod corresponding to one frame.
 5. The display device of claim 1,wherein the driver is configured to transmit the data signal to thedisplay panel for the address period of each of the sub-fields; theplurality of sub-fields comprise first to nth sub-fields, where n is anatural number of 2 or greater, arranged according to the timingsequence within the current frame; and the data signal transmitted tothe display panel during the address period of the first sub-field andthe data signal transmitted to the display panel during the addressperiod of the nth sub-field are equal to each other.
 6. The displaydevice of claim 1, wherein the driver is configured to transmit the datasignal to the display panel for the address period of each of thesub-fields, and the driver is configured to transmit one of m data bits,where m is a natural number of 2 or greater, to the display panel. 7.The display device of claim 6, wherein the plurality of sub-fieldscomprise (m+1) sub-fields, the (m+1) sub-fields comprise first to(m+1)th sub-fields arranged according to the timing sequence within thecurrent frame, and the data bit transmitted to the display panel duringthe address period of the first sub-field and the data bit transmittedto the display panel during the address period of the (m+1)th sub-fieldare equal to each other.
 8. The display device of claim 7, wherein the mdata bits have weights, respectively, and the data bit transmitted tothe display panel during the address period of the first sub-field andthe data bit transmitted to the display panel during the address periodof the (m+1)th sub-field have the highest weight among the m data bits.9. The display device of claim 8, wherein the m data bits comprise firstto mth data bits, and an ith data bit, where 1 <=i <=m, among the firstto mth data bits, has a weight of 2^(i-1).
 10. The display device ofclaim 7, wherein each of the pixel rows comprises one or more pixels,and each of the first to (m+1)th sub-fields further includes a lightemission period in which the pixels emit light or not according to thedata bit transmitted to the display panel during the address periodincluded in each of the first to (m+1)th sub-fields.
 11. The displaydevice of claim 10, wherein a sum of the length of the light emissionperiod of the first sub-field and the length of the light emissionperiod of the (m+1)th sub-field, for each of the pixel rows, is equal toeach other.
 12. The display device of claim 11, wherein the length ofthe light emission period of the first sub-field or the length of thelight emission period of the (m+1)th sub-field, for each of the pixelrows, is different from each other.
 13. A display device for displayingan image by dividing one frame into a plurality of sub-fields, thedisplay device comprising: a display panel comprising a plurality ofpixel rows; a driver connected to the display panel and for transmittingscan signals or data signals to the display panel; a frame memoryconnected to the driver, for storing externally received image data, andfor transmitting at least some of the image data to the driver; and acontroller connected to the driver and the frame memory, generating acontrol signal and transmitting the control signal to the driver or theframe memory, wherein each of the sub-fields includes an address periodin which the scan signals are transmitted to the respective pixel rows,the controller is configured to transmit the control signal to thedriver to transmit the scan signals to the pixel rows during a currentframe such that the scan signals corresponding to the current frame aretransmitted after, among the image data corresponding to the currentframe, the image data corresponding to the pixel rows are stored in theframe memory, wherein driver is configured to transmit the data signalto the display panel for the address period of each of the sub-fields,and the driver is configured to transmit one of m data bits, where m isa natural number of 2 or greater, to the display panel, wherein theplurality of sub-fields comprise (m+1) sub-fields, the (m+1) sub-fieldscomprise first to (m+1)th sub-fields arranged according to the timingsequence within the current frame, and the data bit transmitted to thedisplay panel during the address period of the first sub-field and thedata bit transmitted to the display panel during the address period ofthe (m+1)th sub-field are equal to each other, wherein each of the pixelrows comprises one or more pixels, and each of the first to (m+1)thsub-fields further includes a light emission period in which the pixelsemit light or not according to the data bit transmitted to the displaypanel during the address period included in each of the first to (m+1)thsub-fields, wherein the m data bits have weights, respectively, lengthsof the light emission periods of the second to mth sub-fields areproportional to weights of the data bits transmitted to the displaypanel during the address periods included in the second to mthsub-fields, and a sum of the lengths of the light emission periods ofthe first and (m+1)th sub-fields is proportional to the weight of thedata bit transmitted to the display panel during the address periodincluded in the first sub-field or the (m+1)th sub-field.
 14. Thedisplay device of claim 13, wherein the data bit transmitted to thedisplay panel during the address period of the first sub-field and thedata bit transmitted to the display panel during the address period ofthe (m+1)th sub-field have the highest weight among the m data bits. 15.A display device for displaying an image by dividing one frame into aplurality of sub-fields, the display device comprising: a display panelcomprising a plurality of pixel rows; a driver connected to the displaypanel and for transmitting scan signals or data signals to the displaypanel; a frame memory connected to the driver, for storing externallyreceived image data, and for transmitting at least some of the imagedata to the driver; and a controller connected to the driver and theframe memory, for generating a control signal, and for transmitting thecontrol signal to the driver or the frame memory, wherein the framememory is configured to receive at least some of the image datacorresponding to a current frame from the respective pixel rows at thesame time when the period of the current frame starts; wherein thedriver is configured to start to transmit scan signals for the pluralityof sub-fields to the display panel after the frame memory starts toreceive the image data corresponding to the current frame; and, whereinthe controller is configured to transmit the control signal to thedriver such that a total time taken for the scan signals to betransmitted to all of the plurality of pixel rows during an addressperiod of the sub-field arranged earliest during the current frame,among the plurality of sub-fields, is longer than or equal to a timetaken for the image data corresponding to the current frame to be allstored in the frame memory.
 16. The display device of claim 15, whereinthe driver is configured to start transmitting all of the scan signalstransmitted during the current frame to the display panel after theframe memory starts to receive the image data corresponding to thecurrent frame.
 17. The display device of claim 15, wherein the timetaken for the image data corresponding to the current frame to be allstored in the frame memory is shorter than or equal to half of the timeperiod corresponding to one frame.
 18. The display device of claim 15,wherein the driver is configured to transmit the data signal to thedisplay panel for the address period of each of the sub-fields; whereinthe driver is configured to transmit one of m data bits, where m is anatural number of 2 or greater, to the display panel; wherein theplurality of sub-fields include first to (m+1)th sub-fields, arrangedaccording to the timing sequence within the current frame; and whereinthe data signal transmitted to the display panel during the addressperiod of the first sub-field and the data signal transmitted to thedisplay panel during the address period of the (m+1)th sub-field areequal to each other.
 19. The display device of claim 18, wherein each ofthe pixel rows includes one or more pixels, each of the first to (m+1)thsub-fields further comprises a light emission period in which the pixelsemit light or not according to the data bit transmitted to the displaypanel during the address period included in each of the first to (m+1)thsub-fields, and a sum of the length of the light emission period of thefirst sub-field and the length of the light emission period of the(m+1)th sub-field for each of the pixel rows is equal to each other. 20.A display device for displaying an image by dividing one frame into aplurality of sub-fields, the display device comprising: a display panelcomprising a plurality of pixel rows; a driver connected to the displaypanel and for transmitting scan signals or data signals to the displaypanel; a frame memory connected to the driver, for storing externallyreceived image data, and for transmitting at least some of the imagedata to the driver; and a controller connected to the driver and theframe memory, for generating a control signal, and for transmitting thecontrol signal to the driver or the frame memory, wherein the controlleris configured to transmit the control signal to the driver such that atotal time taken for the scan signals to be transmitted to all of theplurality of pixel rows during an address period of the sub-fieldarranged earliest during a current frame, among the plurality ofsub-fields, is longer than or equal to a time taken for the image datacorresponding to the current frame to be all stored in the frame memory,wherein the driver is configured to transmit the data signal to thedisplay panel for the address period of each of the sub-fields; whereinthe driver is configured to transmit one of m data bits, where m is anatural number of 2 or greater, to the display panel; wherein theplurality of sub-fields include first to (m+1)th sub-fields, arrangedaccording to the timing sequence within the current frame; and whereinthe data signal transmitted to the display panel during the addressperiod of the first sub-field and the data signal transmitted to thedisplay panel during the address period of the (m+1)th sub-field areequal to each other, wherein each of the pixel rows includes one or morepixels, each of the first to (m+1)th sub-fields further comprises alight emission period in which the pixels emit light or not according tothe data bit transmitted to the display panel during the address periodincluded in each of the first to (m+1)th sub-fields, and a sum of thelength of the light emission period of the first sub-field and thelength of the light emission period of the (m+1)th sub-field for each ofthe pixel rows is equal to each other, wherein the m data bits haveweights, respectively, lengths of the light emission periods of thesecond to mth sub-fields are proportional to weights of the data bitstransmitted to the display panel during the address periods included inthe second to mth sub-fields, and a sum of the lengths of the lightemission periods of the first and (m+1)th sub-fields is proportional tothe weight of the data bit transmitted to the display panel during theaddress period included in the first sub-field or the (m+1)th sub-field,and the data bit transmitted to the display panel during the addressperiod of the first sub-field and the data bit transmitted to thedisplay panel during the address period of the (m+1)th sub-field havethe highest weight among the m data bits.
 21. A display device fordisplaying an image by dividing one frame into a plurality ofsub-fields, the display device comprising: a display panel comprising aplurality of pixel rows; a driver connected to the display panel and fortransmitting scan signals or data signals to the display panel; a framememory connected to the driver, for storing externally received imagedata, and for transmitting at least some of the image data to thedriver; and a controller connected to the driver and the frame memory,for generating a control signal and transmitting the control signal tothe driver or the frame memory, wherein each of the sub-fields includesan address period in which the scan signals are transmitted to therespective pixel rows, the controller is configured to transmit thecontrol signal to the driver to transmit the scan signals to the pixelrows during a current frame such that the scan signals corresponding tothe current frame are transmitted after, among the image datacorresponding to the current frame, the image data corresponding to thepixel rows are stored in the frame memory, wherein a time taken for theimage data corresponding to the current frame to be all stored in theframe memory is shorter than or equal to half of the time periodcorresponding to one frame.